There's an old post by BradB about airbrushing a chip in his Porsche's fender. It's amazing and you can't even see it anymore.
http://www.autopia.org/forum/car-detailing/43937-chip-repair-three-simple-weeks.html
http://www.autopia.org/forum/car-detailing/43937-chip-repair-three-simple-weeks.html